MEMS Silicon Expansion Valve Heads Toward New HVAC Applications

When we last spoke to the people at Microstaq Inc., maker of the silicon Ventillum microelectromechanical systems (MEMS) expansion valve IC, they were busy addressing the requirements of the HVAC field for more efficient fluid control leading to significant energy savings for HVAC OEMs (see “MEMS And Nano Push For Higher System Integration Levels”). They’ve since expanded their presence to retrofitting and refrigeration applications and are preparing for a strategic relationship with a major hot-water heater home appliance manufacturer.

Their newest product based on the Ventillum chip, the SuperHeat controller (Fig. 1), combines the microfluidic chip with a MEMS pressure sensor and with processing and control circuitry from Freescale Semiconductor for accurate flow control for the growing air-conditioning and refrigeration markets. It’s designed to improve HVAC and refrigeration system energy efficiency and reliability, while also enabling predictive system maintenance.

The SuperHeat controller operates with hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) refrigerants, including R410A, R407C, and R22 refrigerants. The Ventillum chip, at 6 by 10 mm, is small enough to work with any refrigerant in an extremely compact package. The compact, easy-to-install module is compatible with virtually all air-conditioning, heat-pump, and refrigeration applications.

According to data from the ARC Advisory Group, the growing HVAC market is forecast to approach $13 billion by next year and will require greater attention to energy conservation and small size. Statements from both Microstaq and Freescale Semiconductor point out that their implementation of the SuperHeat controller will offer higher energy efficiency for HVAC systems. Also, it won’t contribute to ozone depletion or global warming. It will enhance heat-pump performance and enable low-maintenance and high-reliability levels as well.

“We’re working with a major home appliance (hot-water heater) manufacturer who is considering using our silicon expansion valve (SEV) technology. That company may well be introducing their appliance with our product next year,” adds Kaina.

Big Energy Savings From A Small Valve Microstaq’s breakthrough all starts with the Ventillum microfluidic SEV, which makes the chip ideal as a proportional refrigerant expansion valve (Fig. 2). The SEV consists of just two moving parts, compared to conventional valves that have been around for decades with five moving parts. At 0.3 cm3, the device is 100 times smaller and weighs around 150 times less than a conventional solenoid valve.

The SEV-1400, SEV-1800, and SEV-2400 address respective equivalent orifice sizes of 1.4, 1.8, and 2.4 mm, at respective nominal capacities of an R40a refrigerant of 1.5, 3, and 5 tons. In an expansion-valve application for air conditioning and refrigeration, access to pressure at the site of the expansion orifice allows accurate calculation of superheat and prediction of phase-change location in the refrigeration circuit.

The SEV is compatible with oils of polyolester, alkybenzene, and mineral and features a response time of less than 0.5 s. It operates from either 12 V dc or 24 V ac and consumes 8 W maximum (4 W steady state). Additionally, it has a maximum operating pressure drop of 450 pounds per square inch (psig) and a maximum working pressure of 650 psig (44.8 bar). Burst pressure is rated at 3250 psig, and its lifetime is a minimum of 1 million cycles.